Quantitative characterization of the contribution of electrogenerated active species for NH+ 4-N oxidation on Ti/RuO2-IrO2 anode

Abstract

The contribution of active species for ammonia nitrogen (NH4+-N) oxidation has received much attention in recent decades through electrocatalytic oxidation (EO) technology. Here we describe the strong NH4+-N removal capacity (more than 98 %) with NaCl as electrolyte of Ti/RuO2-IrO2 anode. Electrochemical tests were used to characterize the excellent NH4+-N degradation performance of Ti/RuO2-IrO2 anode in presence of chlorides. The values of electron transfer number (n = 1.02) and transfer coefficient (α = 0.42) show that the reaction is in the diffusion control stage, which is more conducive to the degradation of NH4+-N. Additionally, three active species (•OH, Cl•, and ClO•) formation is related to the adsorption energy (obtained by density functional theory (DFT) calculation) during the electrolysis process. The difference charge density and density of state (DOS) calculation indicate that the O − in ClO• is more likely to break and react with pollutants in water, which is consistent with the results of active species detection experiments. The combination of kinetics (Tafel) and thermodynamics (adsorption energy) shows that the variation of Tafel slope is affected by the coverage of active species on the electrode surface.